During the processes of normal embryonic growth and development, it is vital that both cytoplasmic streaming and cell migration occur in a specific and proper manner. The molecular basis for cell motility and for the intracellular transport of information and material is not well understood. The proposed study is an investigation of the contractile proteins of mammalian adult and fetal brain using biochemical and biophysical techniques including ultracentrifugation, light scattering, electrophoresis, viscometry, electron paramagnetic resonance (EPR), and assays for ATPase, a myosin-kinase and -phosphatase. The aggregation of brain myosins will be examined; the configuration of myosin oligomers and the conditions conducive to ordered aggregation will be determined as a function of development. The polymerization characteristics of purified fetal and mature brain actins will be determined and analysed by means of saturation transfer EPR spectroscopy. Regulation of this cytoplasmic actomyosin complex will be studied in detail; possible control points for the protein-mediated Ca ions-sensitivity of the actomyosin Mg ions-ATPase will be examined in order to determine the molecular basis for reglation of cytoplasmic motility. This research should increase our understanding of cytoplasmic streaming in developing nerve cells and should shed new light on molecular processes which may lead to congenital defects in the central nervous system.